System of communication



Dec. 20, 1938. J. c. BATCHELOR 2 Shets-Sheet 1 Filed Jan. 31, 1935 D1938- J. c. BATCHELOR 2,140,730

- SYSTEM OF COMMUNIGATIQN Filed Jan. 31, 1955 2 Sheets-Sheet 2 F .5- aINVENTOR.

Patented Dec. 20, 1938 UNITED STATES PATENT OFFICE 2 Claims.

My invention relates to a system of communication, and, moreparticularly, to such a system wherein broadcast communication isaccomplished by meter waves in areas adjacent large 5 centers ofpopulation, and the broadcasting stations in a plurality of such centersof population are interconnected by radio beam communication using meteror shorter waves.

It has been proposed in the visual communication art to providebroadcasting transmitters in metropolitan areas, and, using wave lengthsof the order of 6 meters, to transmit programs, such as televisionimages, with sumcient power to cover distances as great as 40 miles, orperhaps more.

Furthermore, it has been proposed, when two or more such broadcastingtr-ansmittersare operated in two or more such metropolitan areas, toprovide along the lines joining the two areas, a succession of radioreceiving and rebroadcasting installations operating on wave lengths ofthe order of one meter and having sufficiently directionalcharacteristics that only a relatively small amount of power is requiredfor satisfactorily repeating the signals received from the nextpreceding station.

Inasmuch as the number of repeater stations in such an installation isrelatively large, it is essential that the receiving element of eachrepeater station be operated at a point of relatively high fieldintensity in order that the ratio of communicated signal to extraneousnoise signal will be of sufficiently high order to prevent undueaccumulation of noise in the transmitted signal upon successiveretransmissions. Because of this limitation and the limitation imposedby the optical nature of the signals transmitted, the practical limit ofthe inter-val between transmitter stations in a long series of relaystations appears with present technique to be about 20 miles. It istrue, however, that if the signal radiated from any given repeaterstation were not to be used for successive retransmissions, it would bepossible to reproduce an image from a signal of considerably lower fieldintensity, and in many instances it is possible to reproduce an imagedirectly from a signal received from a low power beam transmitter suchas are used in repeater systems at distances as great as 60 miles. Thusit is apparent that, when a series of repeater stations are employedalong a line joining two broadcast transmitters between whichintercommunication is desired, the service range along the axis oftransmission is considerably smaller when a number of repetitions areused than would be required were an image to be reproduced directly fromthe signal transmitted by any given repeater transmitter.

Moreover, with broadcast transmitters serving only the metropolitanareas, it is clear that a large percentage of the population residing in5 rural districts will be denied the privilege of receiving televisionimages except in such cases where receiving apparatus may be useddirectly along the axis of a beam repeater system. In this latter case,a receiver capable of responding to radiation of the wave length beingused by the repeater stations will be capable of reproducing images fromintercepted signals.

With the foregoing in mind, it is an object of my invention to providevisual communication service and the like to a larger portion of therural population than has heretofore been possible. This and otherobjects will be apparent upon examination of the following descriptionof my invention.

In accordance with my invention, I have provided a televisionbroadcasting station of a nondirectional type, associated with which isa directional radio transmitter, by means of which I am enabled totransmit a beam of television signals in a direction not coincident witha line between the broadcast transmitting station and another similarbroadcast transmitting station located at a remote point, and with whichcommunication is desired. Thus, even in the absence of the curvature ofthe earths surface, and with suiiicient power provided, no signal wouldbe receivable at the remote point from the first beam transmitter. Alongthe axis of this first beam transmitter, I have provided directionallyresponsive receiving apparatus at a point where the field intensity fromthe beam. transmitter is of an appropriate value greater than the noiselevel at the point of reception. Associated with this receivingapparatus I have provided a second beam transmitting apparatus directedin a direction having substantially equal divergence with but in anopposite sense to the divergence of the first beam transmitter from theline connecting the first broadcast transmitter and the remote point.

Similarly, I have provided a plurality of receiver-transmitter repeaterstations each having a definite-angular divergence from the line betweenthe first broadcast transmitter and the remote point, each cooperatingwith the preceding one to provide retransmission of the signal, andalternate stations transmitting over adjacent areas having parallelaxes. Terminating this succession of repeater stations, I have provideda final repeater station whose transmitter is directed towarddirectional receiving means associated with the broadcasting station atthe remote point, whereby signals radiated from the first broadcastingstation may be relayed to and retransmitted by the remote broadcastingstation.

Thus, by providing less than 15 percent more repeater stations thanwould be required for transmission along lines joining variousbroadcasting stations, I am enabled to serve an area comprising arelatively wide strip of territory along the lines joining the variousbroadcast stations.

Further, in accordance with my invention, I have in some instancesprovided a plurality of repeater stations interconnecting a plurality ofbroadcasting stations, the repeater stations being disposed in ageometrical configuration such that certain adjacent repeater stationsserve areas which are substantially non-overlapping.

In order to make possible a clearer understanding of my invention,attention is directed to the accompanying drawings, of which Figure 1represents a plan View of a system in accordance with my invention;Figure 2 is a plan view of a repeater station adaptable to my system;Figure 3 is an elevation view of a modification of the embodiment shownin Figure 2; Figure 4 is an elevation view of a still further modifiedrepeater station; and Figure 5 is a plan view of a modified form of mysystem.

Referring to Figure 1, a television scanner l, or other source ofelectrical signals corresponding to intelligence to be communicated, isprovided whereby signals may be impressed upon a radio transmitter 2operating on a wave length of, say, 6 meters whereby signals may beradiated by the non-directional radiator 3 over the area enclosed in thedotted circle 4, which may have a radius of 20 miles. Thus, if theradiator 3 is located in the city of New York, broadcast service may beprovided for the entire metropolitan area of that city.

Similar signals from the output of the scanner l are conducted to thetransmitter 5, which is in turn connected to the directional radiator G.A second broadcast transmitter 1 provides a radio frequency carrier wavewhich may be radiated by the non-directional radiator 8, and is locatedin a second center of population, such as, for example, Philadelphia;the transmitter I is adapted to be modulated by signals from the radioreceiver 9, the input of which is taken from the directional receivingantenna Ill. Thus we may draw the line H between the radiator 6 and thereceiving antenna Ill to represent the axis along which communication isrequired, and which line I shall refer to as the mean axis oftransmission.

Returning now to the radiator 6, it may be seen in Figure 1 that anangle l2, which may be 30 degrees, exists in the horizontal planebetween the line H and the axis of transmission iii of the radiator B. Adirectional receiving antenna it is provided along the axis oftransmission iii of the radiator 6, and is so disposed as to receiveenergy radiated by the radiator 6. In order to reach the receivingantenna [4 from the radiator 6, energy must in many instances,particularly in the example shown, traverse essentially metropolitanterritory where buildings and other structures cause more rapidattenuation of radiation than is encountered by radiation over ruralterritory, and therefore in this embodiment of my invention I havelocated the antenna M at a distance of 10 miles from the radiator 6.This distance may under favorable conditions be substantially increased.The antenna is is connected to a combined receiver-transmitter l5 whichmay consist of conventional radioreceiving apparatus adapted to modulatea radio transmitting apparatus, but, alternately, it may be a radiofrequency amplifier designed to amplify in power the energy receivedfrom the antenna M. The transmitter portion of the receiver-transmitteri5 is in turn connected with the directional radiator !8 adapted toradiate energy at an angle on a horizontal plane from the line 13 oftwice the angle I2 and at an angle ll from the line H substantiallyequal to the angle [2. If clockwise angles are considered to bepositive, and counterclockwise angles are considered to be negative insense, then with reference to the line I 1 between the two broadcastingstations, the axis of transmission [3 of the radiator 6 is positivethirty degrees, and the axis of transmission it of the radiator I6 isnegative thirty degrees, the angle between the axes l3 and I9 being thusdouble the angle l2. Thus there is provided a repeater station 18comprising the directional receiving antenna M, the receiver-transmitteri5 and the directional radiator I6. A second directional receivingantenna 20 is provided along the axis of transmission E9 of the radiator16 at a distance of, say, 20 miles from the radiator l6, which antennaprovides an input signal to the receivertransmitter 2| which in turnprovides energy to the directional radiator 22 having an axis ofradiation 23 parallel to the axis of radiation [3 or in a sense ofpositive 30 degrees in the example shown. A second repeater station 2'1,then, is constituted by the antenna 20, the receivertransmitter 21 andthe radiator 22.

At a point, say, 20 miles along the axis of transmission 23 of theradiator 22 is provided another repeater station 25 similar to therepeater station i8 and so disposed as to receive energy from adirection substantially parallel to the direction from which energy isreceived by the antenna I4, and, further, adapted to radiate energy in adirection substantially parallel to the axis of radiation l9 of theradiator 56, or in a sense of negative 30 degrees in the example shown.Thus the axis of radiation of the repeater 25 may be represented by theline 26.

At a point of the order of 20 miles distant from the repeater station 25is provided an additional repeater station Z'l similar to the repeaterstation 24, adapted to receive energy from the station 25 and totransmit energy controlled by said received energy to the directionalreceiving antenna H! in a direction parallel to the axis of radiation 23of the repeater station 24, or in a sense of positive 30 degrees in theexample shown. The transmitted energy in travelling from the radiator 38to the receiving antenna ii in the example shown is required to traversemetropolitan territory and I have therefore in the example located thereceiving antenna it at a point of the order of 10 miles distant fromthe radiator 38.

Thus I have provided a system whereby controlled energy may becommunicated from the scanner 4 to the transmitter l and radiatedbroadcast over the area described by the dotted circle 28 which in thisembodiment is presumed to represent the city of Philadelphia.

It may be recognized that, in order to maintain the overall ratio ofsignal to noise at a sufficiently low value throughout the repetitions,it

is necessary to locate successive repeater stations at pointssufiiciently close to preceding stations to maintain a relatively greatfield strength at the receiving antenna of the repeater station. Thus,if we take as an example the repeater station 24 and indicate its fieldintensity distribution in the conventional Way, we may show, forexample, the line 29 along which the field intensity is 100 rnillivolts,the line 30 along which the field intensity is 10 millivolts, the line3| along which the field intensity is one millivolt and the line 32along which the field intensity is 100 microvolts. For the purpose ofreceiving a sumciently strong signal at the repeater station 25, it maybe desired that the received field intensity be of the order of 10millivolts, necessitating locating the station 25 approximately at theintersection of the line 30 and the axis of radiation 23, whereas, sinceit is possible to provide satisfactory receiving equipment capable ofoperating on a signal of the order of 100 microvolts, a receiver 58 maybe located as shown in connection with the receiving antenna 33 and theimage reproducer 34 whereby satisfactory reception of transmitted imagesmay be realized at a point outside of the area enclosed by the circle23. Similarly, television receiving apparatus 35 and 35 may be providedat various points within the zone of coverage of the radiators 6, I6,22, 31 and 38. It may be seen that, assuming the maximum sensitivity ofa receiver is 100 microvolts, the area served by my system is that areaincluded within the lines 4, 28 and 32, and this area has, at arelatively small cost, been increased appreciably over that area whichwould be served were the axes of reception and transmission of therepeater stations separated by 180 degrees, or, in other words,co-linear.

Referring now to Figure 2, in which is shown a plan view of a repeaterstation which may to advantage be employed in my invention, aparaboloidal reflector 39 is supported near the top of the pole 49 bythe wooden members 4| in a manner such that the axis of reception of thereflector 39 is co-linear with the axis of transmission of the nextpreceding radiator in the system (not shown in Figure 2). At the focusof the reflector 39 is disposed an energy-receptive antenna 43, Whichmay be a dipole or any other suitable type, and a transmission line 44is provided leading from the antenna 43 through the opening 45 in thereflector 39 to the box 46, which is attached to the pole 49, and whichcontains a radio receiver excited by the antenna 43. The output of thereceiver is used to modulate a radio transmitter also provided in thebox 46. Batteries may also be provided within the box 46 for operatingthe receiver and the transmitter, or, as an alternate method, a powerline may run to the box 46.

From the radio transmitter in the box 46 is a transmission line 47 whichcommunicates power to the radiating antenna 48, which may be a dipole orother suitable type, situated at the focus of the paraboloidal reflector49 having an axis of radiation as shown by the line 50. The reflector 49is supported upon the pole 4B in a manner similar to the reflector 39.Thus a unit is provided comprising a directional receiver and adirectional transmitter, the latter modulated by the former, capable ofreceiving energy from one direction and transmitting energy proportionalto the received energy in a direction not co-linear with the directionfrom which energy is received.

The height of the pole is chosen from a number of considerations; theheight should be relatively large as compared with the wave length ofthe received and radiated energy in order to avoid interference effectsfrom the surrounding terrain; moreover, the height of the pole chosenwill largely determine the radius of communication possible, because ofthe quasioptical characteristics of the wave-lengths used.

For example, with a height of 100 feet, a range of approximately 12miles may readily be realized, and with both receiving and transmittingantennae elevated 100 feet above the surface of the earth, the rangewill be increased to approximately 24 miles. These ranges, it should beunderstood, refer to the useful range as a repeater station; usablesignals for direct reception are transmitted over appreciably greaterranges, and in many instances, even beyond the optical horizon.

Figure 3 represents a modified form of my repeater station wherein aplurality of paraboloidal reflectors 5|, 52 and 53 are provided, and allare so directed as to receive energy radiated from a preceding repeaterstation and focus that received energy upon the receiving antennae 54,55 and 56 which are in turn coupled to the transmission line 44 in amanner such that the signals received by all of the antennae areimpressed upon the transmission line in phase. The received energy isthen conducted by the transmission line 44 to the receiver-transmitterof the box 46 and energy is communicated by the transmission line 41 andradiated by the radiator 49 in the reflector 49 in a manner similar tothat described in connection with Figure 2.

Figure 4 shows a further modified repeater station in which aparaboloidal reflector 5'! of relatively large dimensions is providedforthe purpose of receiving a relatively great amount of energy from atransmitter which is directed along the axis of reception of thereflector 51, and that energy is in turn reflected upon the receivingantenna 43, communicated along the transmission line 44 to thetransmitter-receiver in the box 45, the output of which transmitter iscommunicated by the transmission line 41 to the radiator 48 in thereflector 49 which may be of smaller size than the reflector 51. Thus,in both Figure 3 and Figure 4, the effective aperture of the receivingreflector is greater than the effective aperture of the transmittingantenna.

It may be seen that various modifications are possible without departingfrom the spirit of my invention. For example, as shown in Figure 5, theinitial unit of the interconnection between the scanner I and thetransmitter 1 may be the non-directional transmitter 2, and the repeaterstation l8 may be located within the service area of the transmitter 2,thereby eliminating the cost of the initial beam transmitter.

Further, in Figure 5, the repeaters have been disposed in a manner suchthat their locus constitutes substantially an arc of a circle.

Such a configuration is of value when a great preponderance ofpopulation lies in one sense with respect to the line between thebroadcast ing transmitters being interconnected, and with such a systemit is clear that territory on one side only of that line is served.Moreover, it is desirable in certain conditions to employ a plurality ofconfigurations of stations, particularly on long distance relaytransmission lines. For example, it may be desirable on certain longlines to employ the configuration of Figure 1 for a given distance,following which co-axial repeaters are used through a sparsely settledarea for some distance. Then, when the line passes a community havingappreciable density of population, an arcuate form may be employedhaving its center of curvature on the side of the line opposite thecommunity. Immediately thereafter an arcuate form having its curvaturein the opposite sense may be employed to serve another community,following which another group of co-aXial repeaters may be employed overterritory having few inhabitants. Thus, it is clear that variouscombinations of geometrical configurations may be used in my systemwithin the spirit of my invention.

Furthermore, various degrees of directionality and various angles ofdivergence of transmitters may be found advantageous. For example, whenvery sharp bundling of radiation from the repeater station is used, theangle of divergence between my repeater stations will be small, whereas,when it is feasible to allow substantial spreading of the radiation, andthe population along the line of transmission is relatively dense, itwill often be advantageous to use angles of divergence of more thanthirty degrees.

Still further, the specific types of radiators and reflectors shown areby no means the only ones adaptable to my invention; any type ofradiator and reflector may be applied in a system employing myprinciple. Moreover, the wave-lengths specified have been chosen merelyfor example as being wave-lengths which are used at present for suchcommunication; any of the wave-lengths which follow optical laws in anyrespect and which are designated as meter waves, decimeter waves,centimeter waves and infra-red rays may be employed to advantage in myinvention.

It may be seen, further, that it is not essential that the transmitter 2in Figure 1 be used in connection with the scanner 1. It is possible toutilize the relay system of my invention when a scanner is used at apoint where local broadcasting is not desired, yet the degree ofcoverage possible using my invention may be desirable between thescanner I and the remote transmitter i. In this case, the omission ofthe transmitter 2 is entirely within the scope of my invention.

I claim.

1. A television system comprising means for analyzing an image,broadcasting means remote from said analyzing means, and a plurality ofdirectional repeater stations having predetermined field intensitydistribution characteristics whereby signals from said analyzing meansmay be communicated to said broadcasting means, at least several of saidrepeater stations being so disposed that energy radiated thereby crossesthe line joining said analyzing means and said broadcasting means ateach successive retransmission, the angle between said line and thedirection of radiation of said energy being such and so related to saiddistribution characteristics that the areas served by alternate repeaterstations are substantially contiguous but non-coincident.

2. A television system comprising means for analyzing an image,broadcasting means remote from said analyzing means, a plurality ofdirectional repeater stations having predetermined field intensitydistribution characteristics adapted to communicate signals from saidanalyzing means to said broadcasting means, at least several of saidrepeater stations being so disposed that energy radiated thereby crossesthe line joining said analyzing means and said broadcasting means ateach successive retransmission, the angle between said line and thedirection of radiation of said energy being such and so related to saiddistribution characteristics that the areas served by alternate repeaterstations are substantially contiguous but non-coincident, and

image receiving means within the field of at 0 least one of said areasserved.

JOHN C. BATCI-IELOR.

